Electric shock occurs upon contact of a (human) body with any source of electricity that causes a sufficient current through the skin, muscles, or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable.
Other issues affecting lethality are frequency, which is an issue in causing cardiac arrest or muscular spasms. Very high frequency electric current causes tissue burning, but does not penetrate the body far enough to cause cardiac arrest (see electrosurgery) Also important is the pathway: if the current passes through the chest or head, there is an increased chance of death. From a main circuit or power distribution panel the damage is more likely to be internal, leading to cardiac arrest. //wikipedia